1. Field of the Invention
This invention relates to an adhesive tape, and more particularly to an adhesive tape which may be conveniently used as a sealing tape for containers made of, for example corrugated cardboard or as a splicing adhesive tape for butt joining seams of elongated paper, cloth, film or the like.
2. Prior Art
Hithertofore there has been known an adhesive tape of the type for use as a splicing adhesive tape comprising a film of cellophane paper, kraft paper, polypropylene or the like as a substrate and a pressure sensitive adhesive applied to one side or both sides of the film. The adhesive tape of this type, however, has a disadvantage that it has less strength against a force applied in a lateral or transverse direction so that it can often readily be torn or cut off, particularly when it has a slight rent on its edge. To avoid such disadvantage there has been used a film of polyesters as a substrate which has relatively high strength. However, polyester films are quite expensive. Therefore, the tape of such type has not been widely used.
Alternatively, an adhesive tape for sealing, for example corrugated cardboard containers has been known in which paper, fabrics, a polypropylene film or a polyvinyl chloride film is used as a substrate, a pressure sensitive adhesive being applied to one side or both sides of the substrate. The adhesive sealing tape of the type in which paper is used as a substrate is not strong enough to seal containers filled with relatively heavy contents. Accordingly, a reinforced paper backed with various plastic films or fablics has been used as a substrate material. However, the reinforced paper adhesive tape has drawbacks that it is quite difficult to cut by hand or hands and even if it can, the tape has a tendency to cut zigzag or in a slanting direction. Therefore, one has to utilize a special cutting device, which results in inefficient packing operation. In addition, when a reinforcing plastic film or fabric is adhered to the substrate paper, it is generally required to use a special adhesive or primer due to weak affinity between the reinforcing material and the substrate paper. Consequently, complicate steps for applying adhesives and for receiving solvents are necessarily involved for the production of such reinforced paper adhesive tape. In the meanwhile, the adhesive sealing tape of the type in which a polypropylene film or a polyvinyl film is used as a substrate, has inferior properties at low temperature such as brittleness. Furthermore, polyethylene or polyvinylchloride has large stiffness as shown by bending test as well as large coefficient of tensile elasticity at an elongation of 5%. Hence, when the tape comprising a film of these materials is used for sealing packages containing cold contents such as frozen food or used under low temperatures, the bent portions of the tape tends to stretch so that the tape gets turned or tucks up and peels off out of the packages.